On Wed, Jun 11, 2014 at 10:43:30AM -0700, Stéphane Marchesin wrote: > On Tue, Jun 10, 2014 at 4:04 AM, Thierry Reding > <thierry.reding@xxxxxxxxx> wrote: > > From: Thierry Reding <treding@xxxxxxxxxx> > > > > Currently the tiling parameters of buffer objects can only be set at > > allocation time, and only a single tiled mode is supported. This new > > DRM_TEGRA_GEM_SET_TILING IOCTL allows more modes to be set and also > > allows the tiling mode to be changed after the allocation. This will > > enable the Tegra DRM driver to import buffers from a GPU and directly > > scan them out by configuring the display controller appropriately. > > I was wondering why not support the new tiling modes on creation as > well, I guess because you don't have room for height in the creation > ioctl? Yes, back at the time when the GEM_CREATE IOCTL was added we only left enough room for "flags", so it'll be difficult to add support for the newer tiling modes. One possibility that I see is to extend struct drm_tegra_gem_create in a backwards-compatible way and make new fields dependent on some new flag, somewhat like this: #define DRM_TEGRA_GEM_CREATE_BLOCK_LINEAR (1 << 3) struct drm_tegra_gem_create { __u64 size; __u32 flags; __u32 handle; __u32 height; __u32 pad; }; Then the DRM driver can parse the height field only if the BLOCK_LINEAR flag is set. To be honest, though, I'd prefer to deprecate the flags at creation if these patches get merged so that we can have a standard way of setting these rather than a few. Do you see any particular advantages in specifying the tiling mode at creation time? > > diff --git a/include/uapi/drm/tegra_drm.h b/include/uapi/drm/tegra_drm.h > > index b75482112428..0829f75eb986 100644 > > --- a/include/uapi/drm/tegra_drm.h > > +++ b/include/uapi/drm/tegra_drm.h > > @@ -129,6 +129,27 @@ struct drm_tegra_submit { > > __u32 reserved[5]; /* future expansion */ > > }; > > > > +#define DRM_TEGRA_GEM_TILING_MODE_PITCH 0 > > +#define DRM_TEGRA_GEM_TILING_MODE_TILED 1 > > +#define DRM_TEGRA_GEM_TILING_MODE_BLOCK 2 > > + > > +struct drm_tegra_gem_set_tiling { > > + /* input */ > > + __u32 handle; > > + __u32 mode; > > + __u32 value; > > This seems to only be used for height, if so should it be called height? The idea here was to have a generic name here so that it could be more easily extended if/when newer tiling modes are introduced. Thierry
Attachment:
pgpcDbVxjPQU4.pgp
Description: PGP signature